In process automation technology, field devices are often employed, which serve to register and/or influence process variables. Examples of such field devices are fill level measuring devices, mass flow measuring devices, pressure and temperature measuring devices etc., which, as sensors, register the corresponding process variables, fill level, flow, pressure, and temperature, respectively.
In principle, all devices which are used near to the process and which deliver or work with process-relevant information are referred to as field devices.
A plurality of such field devices is produced and sold by the firm, Endress+Hauser.
Applied for determining the conductivity of a liquid medium are inductively working sensors, which have a transmitting coil, as well as a receiving coil. The receiving coil is arranged at a distance from the transmitting coil. Produced by the transmitting coil is an alternating electromagnetic field, which acts on the charged species (e.g. ions) in the liquid medium, and brings about a corresponding electrical current flow in the medium. Through this electrical current flow, an electromagnetic field arises at the receiving coil, which induces a received signal in the receiving coil. This received signal can be evaluated and taken into consideration for determining the conductivity of the liquid medium.
When inductively measuring conductivity, a risk exists that, as a result of coil defects (such as, for example, winding shorts, leakage currents or damage to the coil, etc.), defective measured values will be ascertained, and that the defectiveness of these measured values will not be recognized.